Network virtualization technologies for defining multiple logical networks on a single physical network are currently used. One of such network virtualization technologies is a tag-based virtual local area network (VLAN). In tag-based VLAN, a tag which includes a VLAN identifier (VLAN-ID) is inserted into a frame. A communication apparatus (for example, a layer 2 switch) for forwarding frames controls forwarding destinations of the frames by referring to tags so that frames for different VLANs are not mixed together. Tag-based VLAN is used, for example, in a layer 2 network at a data center in order to separate frames with respect to each user.
In regard to bandwidth control among VLANs, a method has been proposed in which a maintenance terminal sets, in a layer 2 switch, bandwidth assigned to individual VLAN groups. In addition, a method has been proposed in which a bandwidth ratio among VLAN groups is set in a layer 2 switch so as to enable automatic bandwidth control according to the band ratio. Further, a proposed communication apparatus capable of forwarding Internet protocol (IP) packets and layer 2 packets by a single switch generates a table for managing virtual channels with the use of information collected using an address resolution protocol (ARP).
Japanese Laid-open Patent Publication No. 2007-274529
Japanese Laid-open Patent Publication No. 2007-68050
In the case when a communication apparatus performs bandwidth control according to tag information, the following method may be considered. On an output port side, the amount of accumulated frames is managed with respect to each piece of the tag information, and frames including particular pieces of the tag information are discarded. However, classifying frames with respect to each output port according to the tag information leaves the problem of low processing efficiency.
For example, in tag-based VLAN, a VLAN-ID is expressed as a 12-bit number, and 4094 VLAN-IDs after excluding two reserved VLAN-IDs are available for users. In the case of performing processing for individual VLANs on the output port side, it is considered to provide, with respect to each port, multiple buffers corresponding to those VLAN-IDs and a scheduler for controlling transmission order of frames stored in the multiple buffers. However, implementation of such a circuit for each output port leads to problems such as an increase in the processing load at the output port side, an increase in the circuit size, and an increase in the power consumption.